Photometer, principally for photographic and pyrometric purposes



Oct. 8, 1929. F. HIRSCHSON PHOTOMETER, PRINCIPALLY FOR PHOTOGRAPHIC ANDPYROMETRIC PURPOSES Filed Jan. 8, 192'! NIH llll Patented och-s, 1929PATENT OFFICE FRANZ rrmsoiisoiv, or BERLIN, GERMANY PHOTOMETER,PRINCIPALLY FOR IE'HOTOGRAPHIC AND PYROMETRIC PURPOSES Application-filedJanuary 8, 1927, Serial No.

tric measuring-instruments. Devices are also known, whereby theintensity of current, prevailing during the moment of measuring, is notascertained, but a standard intensity of current fixed, from which thecomparisonbrightness is obtained by achange of resist- V ances.

The value of this change in resistance indicates under certainpresumptions the brightness of the lamp.

- This kind of measuringhas the disadvantage, that an equally greatchange in resistance must render different results, if care is not takento eliminate faults arising from the regulating-resistance for therequired measurement and obtaining a standard intensity, which dependsupon theprevailing battery-tension which may vary over'dif'ferentvalues. The object of-the present invention is to provide an arrangementin which the value of the current flowing through the lamp during,photometric measuring, can be exactly ascertained without the employmentof a special,measuring-instrument.

The advantage of direct measurement of the current resides in theelimination of the above described source of errors. My invenrent whichis indirectly used as basis for further measurements as will be moreclearly described hereinafter.

In the system of myinvention an independent resistance of hightemperature-coefli-cient is connected with the circuit formed by thebattery, regulating-resistance and photo.- metric lamp as set forth inmore detail in the following specification. v A separate incandescentlamp is particularly adapted to this purpose, which is however merelyused as resistance and not as source of light and is therefore hereafterreferred to as a resistance-lamp. Heating of the incandescent filamentof this resistancetion utilizes a fixed standard intensity of cur-159,963, and in Germany January 14, 1926.

lamp involves a considerable increaseof its self-resistance, the valueof which can serve as the criterion for the intensity of current andconsequentlyelso for the brightness of the photometric lamp in the samecircuit.

Another arrangement is utilized, whereby this self-resistance of theresistance-lamp can be measured. This is done in a very simple manner bydisconnecting the resistance-lamp from the circuit by means of athrow-overswitch and replacing the same by a suitable adjustableresistance. v

In case of consonance of this resistance with the resistance of theresistance-lamp, the ratio of current is not altered in the totalcircuit and it may be thereby observed, that the photometric lamp isglowing with unchangeable brightness, irrespective of whether the gaugedresistance is connected. with the circuit or the resistance-lamp. Inexecuting. a

measurement, the photometric lamp is first ad usted to the source oflight to be measured and the regulating-resistance alternately connectedwith the circuit in a process of substituting, by actuating a switchingsystem. If this resistance does not correspond with the one of the lamp,this fact is observable by a fluctuation in the brightness of thephotometric lamp and so, withgreat exactness, as this lamp haspreviously been. adjusted to the brightness to be measured, byalteringthe regulating-resistance, the photometric lamp is again'brought to itsformer brightness and the resistance of the resistance-lamp can now beread from the position of the gauged reguletting-resistance. Inpractice, the gaugescale will be arranged in values of brightness 1using the instrument as on optical pyrometer, the instrument may becalibrated in values of temperature. v I

Figure 1 is a cross-sectional view taken through the photometer of myinvention; Fig. 2 is a front View of the photometer with the casingpartially broken aw'ayand illustrating the switching mechanism "therein;Fig. 3 is a wiring diagram showing the arrangement' of circuits for thephotometer; and Fig. 4 is a modified wiring diagram of the circuits forthe photometer. Fig. 5 shows of the source of light to be measured, butin a part of the instrument in its application as pyrometer.

The photometric lamp 1 is observed through. an ocular glass 2, n thefield of view of which a matt disc 3 is visible. It is arranged in wellknown manner behind an.

open, inside blackened tube 4 and receives thus the average brightnessof the pictureangle indicated by dotted lines, Fig. 1. The blackenedpipe has the purpose, to permit only such rays to strike the matt disc,emanatitch button 6 is now pressed down, (Figs s Jand 3 a transfer ofelectrical'connections is effected and the i'esist'ance-lamp 7 is re-.

placed by the regulating-resistance 8,.the adjustment of which servesfor reading the brightness of light as above described- In using theinstrument and optical pyrometer, Fig. 5, a collecting lens 3 isemployed instead of the matt disc, whereby a shar picture of the objectto be measured is obtained in the plane of the incandescent fila-.

ment. In this kind of employment of the instrument, the filament is nottuned on a unifo'rmly 'light back-ground as in the case of the'pyrometer, but tuning is done in such a .manner, that the object to bemeasured ap? pears sharpl in the field of view.' In the d photometeror-photographic purposes, it is s not essential, to measure the lucidityof a cer- 'tain','sharply limited part of a picture, but

' thefaverage total lucidity which" is important for the exposure has tobe ascertained, A

fundamental difierence' between photometer and pyrometer does not exist,as the pyrometercan, upon suitable gauging, ediately be used asphotometer, if the'l cidity of auniform' illuminated surface is. to bemeasured,'as 'for instance the lucidity of a worktable, upon which asheet of white paper is placed.

. Fig. 4. illustrates a modified circuitarrangement for thephotometer ofmy invention. The resistance-lamp 7, and the substitutionregulating-resistance 8 is in this case connected in parallel tothe-photometric. lamp 1. The operation of the circuitof Fig, 4 is.

the same as in connection with Fig. 3. The

4 J0 shuntv 9 of predetermined ,value 'as used in 3 may be omitted inthe arrangement of 1g'. 4.; 1

' As the exactness of the measurement de-' upon the extent of the changeinresistafieof theresistance-lam the latter is photometric lamp.

advantageously so selected, that its consumption of current is less thantheone of the In this case, slight changes in brightness will beperceptible in the resistance-lamp in form of correspondingly. increasedresistance-changes. in the other lamp. In practice, an exact syntonizingof the conditions of current in both lamps can be obtained thereby, andthe shunt 9 of predetermined value connected parallel to thephotometric-lamp whereby the consump-..

tion of current is increased in a manner e'xactly calculable. To themaximum bright ness coming in question for thephotometric lamp, fullwhite heat will in this case correspond to the resistance-lamp. .Thisshunt 9 to the photometric lamp is illustrated in alibrations areprovided on the exterior of the casing of the photometer adjacent eachof the operating knobs 9. 10 which control the. effective values ofresistances 5 and 8 and direct readings are taken from the instru-- mentby noting the calibrations for any selected setting.

' While I have. certain of its preferred embodiments, 'I desire that itbe understood that modifications described my invention in may be madeand no limitations .upon my in vention are intended other than areimposed by the scope of the appended claims.

I claim 1: In a photometer a circuit containing a battery, "aregulating-resistance, a sphiotometric incandescent lamp connected inseries with said battery andreslstance, an independent resistance ofhigh temperature coeflicient, a regulating and gauged resistance, a.switch connected incircuit with said lamp and resistances and adapted tocut out said resist-- ance of high temperature coefficient from thecircuit and to cut in said regulating and gauged resistance intothe'circuit'for efle'cting photometric measurements.

2. Ina p otometer a circuit containing a battery, airegulating-resistance, a photometric ncandescent lamp connected inseries with said battery and resistance, a second in- 'candescent lamp,a regulating and gauged v resistance, a switch connected in circuit withsaid lamp and resistances and adapted to cut .outsaid secondincandescent lamp from the circuit and to cutin said regulating and ingphotometric measurements.

*3. In a photometer battery, a regulatin -resistance, a photometricincandescent lamp connected in series with said battery and resistance,a second incandescen't lamp, said second lamp having a smaller.consumption of current than said photometric lamp, a regulating andgauged circuit containing a gauged'resistance into the circuit forefiect-.-

resistance, aswitch connected in circuit with 'saidlamp and resistances,andjadapted to 'cut out second incandescent lamp from the circuit andto cut in said regulating and gauged resistance into the circuit foreflect ing photometric measurements.

4. In a photometer a circuit containing a battery, aregulating-resistance, a photoa metric incandescent lamp connected inseries 7 with sald battery and resistance, an lndependent resistance ofhigh temperature 00- efficient, a regulating and gauged resistance,

a switch connected in circuit with said lamp and resistances and adaptedto cut out said resistance of high temperature coeflicient from thecircuit and to cut in said regulating and gauged resistance into thecircuit,.and a shunt resistance connected in parallel to saidphotometric lamp in said series circuit.

5. In a photometer a circuit-containing a battery, aregulatingresistance, a photometric mcandescent'lamp connected in series7 with said battery and resistance, a second.

incandescent lamp, a regulating and gauged resistance, a switchconnected in circuit with said lamp and resistances adapted to cut outsaid second incandescent lamp from the circuit and to cut in saidreghlating and gauged resistance into the circuit, and a syntonizedshunt resistance connected in parallel to said photometric lamp in saidseries circuit 6. In-a photometer a circuit containing a battery, aregulating-resistance, a photometric incandescent lamp normallyconnected in a series circuit with said battery, a second incandescentlamp, said second lamp having

